1. Field of the Invention
The present invention relates generally to medical methods and devices. More particularly, the present invention relates to medical methods and kits for distributing pharmaceutical agents in the adventitial tissue surrounding a blood vessel.
Coronary artery disease is the leading cause of death and morbidity in the United States and other western societies. In particular, atherosclerosis in the coronary arteries can cause myocardial infarction, commonly referred to as a heart attack, which can be immediately fatal or, even if survived, can cause damage to the heart which can incapacitate the patient. Other coronary diseases which cause death and incapacitation include congestive heart failure, vulnerable or unstable plaque, and cardiac arrhythmias. In addition to coronary artery disease, diseases of the peripheral vasculature can also be fatal or incapacitating. Blood clots and thrombus may occlude peripheral blood flow, leading to tissue and organ necrosis. Deep vein thrombosis in the legs can, in the worse cases, requiring amputation. Clots in the carotid artery can embolize and travel to the brain, potentially causing ischemic stroke.
While coronary artery bypass surgery is an effective treatment for stenosed arteries resulting from atherosclerosis and other causes, it is a highly invasive procedure which is also expensive and which requires substantial hospital and recovery time. Percutaneous transluminal coronary angioplasty (PTCA), commonly referred to as balloon angioplasty, is less invasive, less traumatic, and significantly less expensive than bypass surgery. Until recently, however, balloon angioplasty has not been considered to be as effective a treatment as bypass surgery. The effectiveness of balloon angioplasty, however, has improved significantly with the introduction of stenting which involves the placement of a scaffold structure within the artery which has been treated by balloon angioplasty. The stent inhibits abrupt reclosure of the artery and has some benefit in reducing subsequent restenosis resulting from hyperplasia.
Despite such improvement, patients who have undergone angioplasty procedures with subsequent stenting still suffer from a high incidence of restenosis resulting from hyperplasia. Very recently, however, experimental trials have demonstrated that the implanting of stents which have been coated with anti-proliferative drugs can significantly reduce the occurrence of hyperplasia, promising to make combined angioplasty and stenting a viable alternative to bypass surgery.
As an alternative to stent-based luminal drug delivery, the direct delivery of drug into vascular and other luminal walls has been proposed. For some time, the use of intravascular catheters having porous balloons, spaced-apart isolation balloons, expandable sleeves, and the like, have been used for releasing drugs into the inner surface of the endothelial wall of blood vessels.
Congestive heart failure and cardiac arrhythmias, although sometimes related to coronary artery disease, are usually treated differently than are occlusive diseases. Congestive heart failure is most often treated pharmaceutically, although no particular drug regimens have proven to be highly effective. Proposed mechanical approaches for treating congestive heart failure include constraints for inhibiting further dilation of the heart muscle, and pace makers and mechanical devices for enhancing heart function. Cardiac arrhythmias may also be treated with drug therapies, and reasonably effective intravascular treatments for ablating aberrant conductive paths on the endocardial surfaces also exist. No one treatment, however, for either of these conditions is completely effective in all cases.
Of particular interest to the present invention, catheters carrying microneedles capable of delivering therapeutic and other agents deep into the adventitial layer surrounding blood vessel lumens have been described in U.S. Pat. No. 6,547,303, and co-pending application Ser. No. 09/961,079, filed on Sep. 20, 2001, both having common inventorship with but different assignment than the present application, the full disclosures of which are incorporated herein by reference.
Pharmaceutical therapies for coronary artery and other cardiac and vascular diseases can be problematic in a number of respects. First, it can be difficult to achieve therapeutically effective levels of a pharmaceutical agent in the cardiac tissues of interest. This is particularly true of systemic drug delivery, but also true of various intravascular drug delivery protocols which have been suggested. The release of a pharmaceutical agent directly on to the surface of a blood vessel wall within the heart or the peripheral vasculature frequently results in much or most of the drug being lost into the luminal blood flow. Thus, drugs which are difficult to deliver across the blood vessel wall will often not be able to reach therapeutically effective concentrations in the targeted tissue. Second, even when drugs are successfully delivered into the blood vessel wall, they will frequently lack persistence, i.e., the drug will be rapidly released back into the blood flow and lost from the targeted tissues. Third, it is frequently difficult to intravascularly deliver a pharmaceutical agent to remote and/or distributed diseased regions within a blood vessel. Most prior intravascular drug delivery systems, at best, deliver relatively low concentrations of the pharmaceutical agent into regions of the blood vessel wall which are directly in contact with the delivery catheter. Thus, diseased regions which may be remote from the delivery site(s) and/or which include multiple spaced-apart loci may receive little or no therapeutic benefit from the agent being delivered. In particular, most if not all prior intravascular drug delivery apparatus have been unable to deliver the drug over large volumetric regions of tissue, particularly in a manner which achieves relatively consistent drug concentrations. Fourth, delivery of a pharmaceutical agent into the blood vessel wall may be insufficient to treat the underlying cause of disease. For example, delivery of anti-proliferative agents into the blood vessel wall may have limited benefit in inhibiting the smooth muscle cell migration which is believed to be a cause of intimal hyperplasia or cell proliferation characteristic of neoplastic diseases. Fifth, the etiology of the vascular disease may itself inhibit effective delivery of a pharmaceutical agent. Thus, systems and protocols which are designed to deliver drug into blood vessel wall at the site of disease may be limited in their effectiveness by the nature of the disease itself.
For these reasons, it would be desirable to provide additional and improved methods and kits for the intravascular delivery of pharmaceutical agents to treat coronary cerebral, hepatic, peripheral, and other vascular diseases. Such additional and improved methods and kits would preferably also be adaptable to treat non-vascular diseases, including cancers and other neoplastic diseases, diseases associated with particular organs or other compartmentalized tissue regions, and other conditions which might benefit from remote localized delivery of drugs via the vasculature. In particular, it would be beneficial to provide methods which enhance the therapeutic concentrations of the pharmaceutical agents in diseased and other targeted tissues, not just the blood vessel walls. For example, it would be particularly desirable if the methods and systems could provide for an extended volumetric distribution of the delivered pharmaceutical agent including both longitudinal and radial spreading from the injection site(s) in order to provide therapeutic dosage levels of the agent within the heart, liver, or other organ or compartmentalized tissue region. It would be further beneficial if the methods could efficiently deliver the drugs into the targeted tissue and limit or avoid the loss of drugs into the luminal blood flow. Similarly, it would beneficial to enhance the therapeutic concentrations of the pharmaceutical agent delivered to a particular targeted tissue. It would be still further beneficial if the persistence of such therapeutic concentrations of the pharmaceutical agent in the tissue were also increased, particularly in targeted tissues away from the blood vessel wall, including the adventitial tissue surrounding the blood vessel wall. Additionally, it would be beneficial to increase the uniformity and extent of pharmaceutical agent delivery over remote, extended, and distributed regions of the adventitia and other tissues surrounding the blood vessels. In some instances, it would be beneficial to provide methods which permit the delivery of pharmaceutical agents through the blood vessel walls at non-diseased sites within the blood vessel, where the agent would then be able to migrate through the adventitia or other tissues to the diseased site(s). At least some of these objectives will be met by the inventions described hereinafter. Still further, it would be desirable if such intravascular delivery of pharmaceutical agents would be useful for treating diseases and conditions of the tissues and organs in addition to those directly related to the heart or vasculature.
2. Description of the Background Art
U.S. Pat. No. 6,547,803 B2, and published Application 2003/0171734A1 both having common inventorship with but different assignment than the present application, describe microneedle catheters which may be used in at least some of the methods described in the present application. Drug distribution through the collateral circulation in the heart is discussed in Daschner et al. (1986) J. Cardiovasc. Surg. 581-584; Laham et al. (1999) Drug Met. Disp. 27:821-826; Laham et al. (2003) Cath. Cardio. Interv. 58:375-381; and Altman et al. (2003) Lymph. Res. Biol. 1:47-54.